WO2012176669A1 - Separator having heat resistant insulation layers - Google Patents

Abstract

A separator (1) having heat resistant insulation layers, for electric devices, according to the present invention is provided with: a resin porous substrate (2); and heat resistant insulation layers (3) that are formed on both faces of the resin porous substrate, and that comprise heat resistant particles the melting point or thermal softening point of which is not less than 150°C. A parameter (X) indicated by numerical formula (1) has a value not less than 0.15. In this numerical formula, A' and A'' are thicknesses (μm) of each of the heat resistant insulation layers (3) formed on both faces of the resin porous substrate (2), have a relationship of A' ≥ A'' in this case, and C is the total thickness (μm) of the separator (1) having the heat resistant insulation layers. Numerical formula (1)

Description

Separator with heat-resistant insulation layer

The present invention relates to a separator with a heat-resistant insulating layer.

In recent years, a reduction in the amount of carbon dioxide has been strongly desired in order to cope with global warming. In the automobile industry, there is an expectation for reduction of carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV). For this reason, electric devices such as secondary batteries for motor driving that hold the key to practical use are being actively developed.

In particular, lithium ion secondary batteries are considered suitable for electric vehicles because of their high energy density and high durability against repeated charge and discharge, and there is a tendency for higher capacity to be further developed. Therefore, ensuring the safety of lithium ion secondary batteries has become increasingly important.

A lithium ion secondary battery generally includes a positive electrode in which a positive electrode active material or the like is applied to both surfaces of a positive electrode current collector, and a negative electrode in which a negative electrode active material or the like is applied to both surfaces of the negative electrode current collector. And the said positive electrode and a negative electrode are connected through the electrolyte layer which hold | maintained electrolyte solution or electrolyte gel to the separator. Thereafter, the positive electrode, the negative electrode, and the separator are accommodated in the battery case.

As the separator, for example, a polyolefin microporous film having a thickness of about 20 to 30 μm is often used. However, such a microporous polyolefin membrane may cause thermal shrinkage due to temperature rise in the battery and a short circuit associated therewith.

Therefore, in order to suppress thermal contraction of the separator, a separator with a heat resistant insulating layer in which a heat resistant porous layer is laminated on the surface of a microporous film has been developed. For example, Patent Document 1 describes that such a separator is used for a wound lithium ion battery, and thermal contraction due to temperature rise in the battery is suppressed.

International Publication No. 2007/066768

However, when the separator described in Patent Document 1 is applied to a flat-plate laminated nonaqueous electrolyte secondary battery, curling occurs at the end of the separator during battery manufacture, and the curled portion remains folded. The problem of being stacked arises. In particular, in the case of a large battery used in an electric vehicle, since the area of one member is large, even a slight strain may lead to problems during operation, resulting in a significant decrease in yield.

The present invention has been made in view of such problems of the conventional technology. And the objective is to provide the separator with a heat resistant insulating layer which can suppress the generation | occurrence | production of a curl and can manufacture a highly reliable electrical device stably.

A separator with a heat-resistant insulating layer according to an aspect of the present invention includes a resin porous substrate and a heat-resistant insulating layer formed on both surfaces of the resin porous substrate and containing heat-resistant particles having a melting point or a heat softening point of 150 ° C. or higher. . The parameter X represented by Equation 1 is 0.15 or more:

In the formula, A ′ and A ″ are the thicknesses (μm) of the respective heat-resistant insulating layers formed on both surfaces of the porous resin substrate, where A ′ ≧ A ″, and C is the value of the separator with the heat-resistant insulating layer. The total thickness (μm).

FIG. 1 is a cross-sectional view schematically showing a flat plate type non-bipolar lithium ion secondary battery according to an embodiment of the present invention. FIG. 2 is a schematic view showing an outline of a separator with a heat-resistant insulating layer in one embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a separator with a heat-resistant insulating layer in one embodiment of the present invention. FIG. 4 is a perspective view schematically showing the appearance of a flat plate type non-bipolar lithium ion secondary battery according to an embodiment of the present invention. FIG. 5 is a schematic diagram for explaining a curl height measuring method in the embodiment. FIG. 6 is a graph showing the relationship between the value of parameter X and the curl height in the separators produced in the examples and comparative examples. FIG. 7 is a graph showing the relationship between the value of parameter Y, curl height, and battery rate characteristics in the separators produced in the examples and comparative examples.

Hereinafter, a separator with a heat-resistant insulating layer for an electric device of the present invention and an electric device using the same will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from actual ratios.

In a separator with a heat-resistant insulating layer for an electric device and an electric device using the same according to an embodiment of the present invention, even when a large flat plate type electric device is used, it is difficult to cause problems when laminating each element, and productivity Will improve. Therefore, an electric device using the separator with a heat-resistant insulating layer of the present embodiment, particularly a nonaqueous electrolyte secondary battery, is excellent as a driving power source or an auxiliary power source for a vehicle.

That is, the electrical device of the present embodiment is not particularly limited as long as it uses a separator with a heat resistant insulating layer described below. In the present embodiment, a lithium ion battery will be described as an example of the electric device.

For example, as a usage form of a lithium ion battery, it may be used for either a lithium ion primary battery or a lithium ion secondary battery. Since it is preferably excellent in high cycle durability, it is desirable to use it as a lithium ion secondary battery for a vehicle driving power source or for portable devices such as a mobile phone.

The separator with a heat-resistant insulating layer can be applied to a flat plate type (flat type) battery. By adopting a flat plate type battery structure, long-term reliability can be secured by a sealing technique such as simple thermocompression bonding, which is advantageous in terms of cost and workability.

Further, when viewed in terms of electrical connection form (electrode structure) in a lithium ion battery, it can be applied to both non-bipolar batteries (internal parallel connection type) and bipolar batteries (internal series connection type). .

Furthermore, the separator with a heat-resistant insulating layer can be applied to a solution electrolyte type battery using a solution electrolyte such as a non-aqueous electrolyte solution. Furthermore, the present invention can also be applied to an electrolyte layer such as a gel electrolyte type battery using a polymer gel electrolyte.

Therefore, in the following description, a non-bipolar lithium ion secondary battery using the separator with a heat-resistant insulating layer of the present embodiment will be described with reference to the drawings.

[Battery overall structure]
FIG. 1 shows an overall structure of a flat plate type (flat type) lithium ion secondary battery according to an embodiment of the present invention. Note that a flat plate type lithium ion secondary battery is also simply referred to as a “stacked battery”.

As shown in FIG. 1, the stacked battery 10 of the present embodiment has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction proceeds is sealed inside a battery exterior material 29. Here, the power generation element 21 has a configuration in which a positive electrode, an electrolyte layer 17, and a negative electrode are stacked. The positive electrode has a configuration in which positive electrode active material layers 13 are disposed on both surfaces of the positive electrode current collector 11. Further, the electrolyte layer 17 has a configuration in which an electrolyte (electrolytic solution or electrolyte gel) is held in a separator. Further, the negative electrode has a configuration in which the negative electrode active material layers 15 are disposed on both surfaces of the negative electrode current collector 12. In other words, the negative electrode, the electrolyte layer, and the positive electrode are laminated in this order so that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other with the electrolyte layer 17 therebetween. ing.

Thereby, the adjacent positive electrode, electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the stacked battery 10 shown in FIG. 1 has a configuration in which a plurality of single battery layers 19 are stacked and electrically connected in parallel. Note that the positive electrode current collector 13 located on both outermost layers of the power generation element 21 is provided with the positive electrode active material layer 13 on only one side, but the positive electrode active material layer may be provided on both sides. That is, instead of using the current collector exclusively for the outermost layer provided with the positive electrode active material layer only on one side, a current collector having the positive electrode active material layer on both sides may be used as it is as the current collector for the outermost layer. In addition, the arrangement of the positive electrode and the negative electrode is reversed from that in FIG. 1 so that the negative electrode current collector is positioned on both outermost layers of the power generation element 21, and the negative electrode active material is disposed on one or both surfaces of the outermost negative electrode current collector. A material layer may be arranged.

The positive electrode current collector 11 and the negative electrode current collector 12 are respectively attached with a positive electrode current collector plate 25 and a negative electrode current collector plate 27 that are electrically connected to the respective electrodes (positive electrode and negative electrode). The positive electrode current collecting plate 25 and the negative electrode current collecting plate 27 are led out of the battery outer packaging material 29 so as to be sandwiched between the end portions of the battery outer packaging material 29. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 are ultrasonically welded to the positive electrode current collector 11 and the negative electrode current collector 12 of each electrode via a positive electrode lead and a negative electrode lead (not shown), respectively, as necessary. Or resistance welding or the like.

The lithium ion secondary battery described above is characterized by a separator. Hereinafter, main components of the battery including the separator will be described.

[Active material layer]
The positive electrode active material layer 13 and the negative electrode active material layer 15 contain an active material, and further contain other additives as necessary.

The positive electrode active material layer 13 includes a positive electrode active material. As the positive electrode active material, for example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Co—Mn) O _2, and lithium—such as those in which some of these transition metals are substituted with other elements Examples thereof include transition metal composite oxides; lithium-transition metal phosphate compounds; lithium-transition metal sulfate compounds. Depending on the case, two or more positive electrode active materials may be used in combination. Preferably, from the viewpoint of capacity and output characteristics, a lithium-transition metal composite oxide is used as the positive electrode active material. A positive electrode active material other than the above may be used.

The negative electrode active material layer 15 includes a negative electrode active material. Examples of the negative electrode active material include carbon materials such as graphite (graphite), soft carbon, and hard carbon; lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ); metal materials; lithium alloy negative electrode materials, and the like. Is mentioned. Depending on the case, two or more negative electrode active materials may be used in combination. Preferably, from the viewpoint of capacity and output characteristics, a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material. Note that negative electrode active materials other than those described above may be used.

The average particle diameter of each of the active materials contained in the positive electrode active material layer 13 and the negative electrode active material layer 15 is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 to 20 μm from the viewpoint of high output. .

The positive electrode active material layer 13 and the negative electrode active material layer 15 preferably contain a binder. The binder used for the positive electrode active material layer 13 and the negative electrode active material layer 15 is not particularly limited. Examples of the binder include polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene / butadiene. Rubber (SBR), isoprene rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and hydrogenated product thereof, styrene / isoprene / styrene block copolymer and Examples thereof include thermoplastic polymers such as hydrogenated products. As the binder, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), Examples thereof include fluororesins such as ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), and polyvinyl fluoride (PVF). Further, as the binder, vinylidene fluoride-hexafluoropropylene fluororubber (VDF-HFP fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluororubber (VDF-HFP-TFE fluororubber), Vinylidene fluoride-pentafluoropropylene fluorine rubber (VDF-PFP fluorine rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene fluorine rubber (VDF-PFP-TFE fluorine rubber), vinylidene fluoride-perfluoro Methyl vinyl ether-tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine rubber (VDF- TFE-based vinylidene fluorine rubber) or the like fluoride-based fluororubber can be cited. Moreover, an epoxy resin etc. are mentioned as a binder. Among these, polyvinylidene fluoride, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. These binders are preferably used for the active material layer because they are excellent in heat resistance, have a very wide potential window, and are stable at both the positive electrode potential and the negative electrode potential. These binders may be used alone or in combination of two or more.

The amount of the binder contained in the active material layer is not particularly limited as long as the amount can bind the active material. However, the amount of the binder is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass with respect to the active material layer.

Examples of other additives contained in the active material layer include a conductive additive, an electrolyte salt, and an ion conductive polymer.

The conductive assistant means an additive blended to improve the conductivity of the positive electrode active material layer or the negative electrode active material layer. Examples of the conductive auxiliary agent include carbon materials such as carbon black such as acetylene black, graphite, and carbon fiber. When the active material layer contains a conductive additive, an electronic network inside the active material layer is effectively formed, which contributes to improvement of the output characteristics of the battery.

Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like.

Examples of the ion conductive polymer include polyethylene oxide (PEO) and polypropylene oxide (PPO) polymers.

The compounding ratio of the components contained in the positive electrode active material layer and the negative electrode active material layer is not particularly limited. The blending ratio can be adjusted by appropriately referring to known knowledge about the nonaqueous electrolyte secondary battery. The thickness of each active material layer is not particularly limited, and conventionally known knowledge about the battery is referred to as appropriate. As an example, the thickness of each active material layer is about 2 to 100 μm.

[Current collector]
The positive electrode current collector 11 and the negative electrode current collector 12 are made of a conductive material. The size of the current collector is determined according to the intended use of the battery. For example, in the case of a large battery that requires high energy density, a current collector having a large area is used. The lithium ion battery of the present embodiment is preferably a large battery, and the size of the current collector used is, for example, a long side of 100 mm or more, preferably 100 mm × 100 mm or more, more preferably 200 mm × It is 200 mm or more. There is no particular limitation on the thickness of the current collector. The thickness of the current collector is usually about 1 to 100 μm. The shape of the current collector is not particularly limited. In the laminated battery 10 shown in FIG. 1, in addition to the current collector foil, a mesh shape (such as an expanded grid) can be used.

There are no particular restrictions on the material constituting the current collector, but metal is preferably used. Specific examples include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals is preferably used. Moreover, the foil by which aluminum is coat | covered by the metal surface may be sufficient. Among these, aluminum, stainless steel, and copper are preferable from the viewpoint of electronic conductivity and battery operating potential.

[Electrolyte layer]
The electrolyte layer 17 has a configuration in which an electrolyte is held at the center in the surface direction of the separator of the present embodiment. By using the separator of the present embodiment, it is possible to suppress the occurrence of curling at the end during stacking, and thus it is possible to stably manufacture a highly reliable battery.

(Separator with heat-resistant insulating layer)
The separator with a heat-resistant insulating layer in the present embodiment includes a resin porous substrate and a heat-resistant insulating layer containing heat-resistant particles having a melting point or a heat softening point of 150 ° C. or higher formed on both surfaces of the resin porous substrate. Further, the separator is characterized in that a parameter X represented by the following mathematical formula (1) is 0.15 or more.

In the formula, A ′ and A ″ indicate the thickness (μm) of each heat-resistant insulating layer formed on both surfaces of the porous resin substrate, where A ′ ≧ A ″. C represents the total thickness (μm) of the separator with a heat-resistant insulating layer.

According to the separator of the present embodiment, it is possible to suppress the warpage of the end portion and the occurrence of curling. Therefore, when the separator of the present embodiment is used, the yield can be improved in the manufacturing process of the flat plate type battery. When the value of the parameter X is less than 0.15, curl cannot be ignored, and particularly when a large flat-plate laminated battery is manufactured, the yield is remarkably lowered.

When the separator described in Patent Document 1 described above is applied to a wound battery, it is difficult to cause problems during stacking due to curling of the separator. However, when applied to a large flat-stacked battery such as a lithium ion secondary battery for an electric vehicle, even a slight strain may lead to problems during the stacking operation because the area of one member is large. For example, as shown in FIG. 2 (a), in the case of producing a large flat plate type battery, the negative electrode 5, the separator 1 and the positive electrode 4 are sequentially conveyed using a lamination hand and laminated at a high speed. It is common. However, since the separator is a relatively soft member, if there is a curled portion on the separator as shown in FIG. 2B during conveyance, the separator is piled up. Then, the turned portion is stepped on, and the curled and turned portion is folded and laminated. In such a case, since the cell is short-circuited, the yield is greatly reduced and the cost is increased.

Therefore, the separator 1 with a heat-resistant insulating layer of the present embodiment has a structure in which the heat-resistant insulating layers 3 are provided on both surfaces of the resin porous substrate 2 as shown in FIG.

Here, it is considered that the cause of the curling of the separator is that the thermal stress remains when the heat-resistant insulating layer is applied to the resin porous substrate and is heated and dried by hot air drying or the like. Specifically, since the resin contained in the resin porous substrate has a large coefficient of linear expansion when heated, the resin porous substrate becomes stretched when heated and dried. On the other hand, since the heat-resistant insulating layer is formed using heat-resistant particles having a melting point or a heat softening point of 150 ° C. or higher, the linear expansion coefficient is sufficiently small in the temperature range of heat drying and hardly expands. For this reason, when the heating and drying after coating is completed and the temperature is returned to room temperature, the resin porous substrate contracts greatly, but the heat-resistant insulating layer hardly contracts. As a result, there is a difference in shrinkage between the resin porous substrate and the heat-resistant insulating layer, the resin porous substrate wants to shrink, and the heat-resistant insulating layer resists the curling in such a manner that the resin porous substrate is wound inside. Will occur.

Therefore, in the present embodiment, the heat-resistant insulating layer 3 is applied to both surfaces of the resin porous substrate 2 so that the thicknesses A ′ and A ″ of the heat-resistant insulating layer 3 are as identical as possible. The balance of shrinkage stress of the heat-resistant insulating layer 3 in the vertical direction can be improved and curling can be suppressed. Further, the thicknesses A ′ and A ″ of the heat-resistant insulating layer 3 with respect to the total thickness C of the separator are controlled to a specific relationship. ing. Thereby, the balance between the internal stress of the resin porous substrate 2 and the shrinkage stress of the heat-resistant insulating layer 3 is improved, and curling can be sufficiently suppressed. The parameter X in the above formula (1) is set to 0.15 or more. Thereby, it becomes difficult to produce a big curl, and the problem of folding and curling during the stacking operation can be solved.

The parameter X represented by the mathematical formula (1) is an index as to whether or not a difference in shrinkage stress due to drying of the heat-resistant insulating layers formed on both surfaces of the resin porous substrate becomes obvious. This means that the difference in shrinkage stress of the heat-resistant insulating layer becomes obvious. When the influence of the difference in shrinkage stress between the heat-resistant insulating layers on both sides is large with respect to the internal stress of the resin porous substrate, curling is likely to occur. For example, the smaller the thickness A ′, A ″ of the heat-resistant insulating layer compared to the total thickness C of the separator, the smaller the value of the parameter X. Also, because the difference in basis weight of the heat-resistant insulating layers on both sides is large, When the difference between the thicknesses of the heat-resistant insulating layers on both sides is large, the value of X is small, In the separator of this embodiment, the value of the parameter X is 0.15 or more, preferably 0.20 or more. When the value of X is less than 0.15, the effect of curl cannot be ignored, and the yield is significantly reduced in the production of large flat-plate laminated batteries. The weight (g / m ² ) of the heat-resistant insulating layer per unit area.

Note that the upper limit of the parameter X represented by the above mathematical formula (1) is not particularly limited as long as curling of the separator can be suppressed, but can be set to 1.0, for example.

Furthermore, in the separator of the present embodiment, the parameter Y represented by the following mathematical formula (2) is preferably in the range of 0.3 to 0.7.

In the formula, X is as defined above, and D is the porosity (%) of the heat-resistant insulating layer 3.

As described above, in the separator of the present embodiment, the larger the value of the parameter X represented by the above formula (1), the less likely the end curl occurs. However, if the thickness (A ′, A ″) of the heat-resistant insulating layer is increased, the value of X increases, but the ion permeability decreases and the rate characteristics decrease. As a result of studying conditions for maintaining high rate characteristics while suppressing the above-mentioned, in addition to the thickness of the heat-resistant insulating layer, the porosity of the heat-resistant insulating layer (D in Formula (2)) dominates the rate characteristics In other words, in order to obtain high rate characteristics while suppressing the occurrence of curling, the two heat-resistant insulating layers are formed on both sides of the porous resin substrate with appropriate pressing force from both sides. If the holding force is too weak or biased, curling is likely to occur, and if the holding force is too strong, the ion permeability decreases and the rate characteristics of the battery decrease. there is a possibility.

The parameter Y expressed by the above mathematical formula (2) is an index of how strong and even the two heat-resistant insulating layers hold both sides of the resin porous substrate. For example, if the pressing force is biased on both surfaces of the porous resin substrate due to the difference in the basis weight between the heat-resistant insulating layers on both surfaces, the value of Y is small. Further, the value of Y is small even when the heat-resistant insulating layer is thin or has a large porosity and therefore the pressing force of the heat-resistant insulating layer is weak. Furthermore, the larger the total thickness C of the separator, the smaller the value of Y. On the other hand, when the heat-resistant insulating layer is thick or has a large porosity, the pressing force of the heat-resistant insulating layer is strong. In the separator of the present embodiment, the value of the parameter Y is preferably 0.3 to 0.7, and more preferably 0.35 to 0.65. If the value of Y is 0.3 or more, curling is unlikely to occur. If the value of Y is 0.7 or less, high rate characteristics can be obtained.

In the above formulas (1) and (2), values measured using a micro gauge can be used as the thicknesses A ′ and A ″ of the heat-resistant insulating layer and the total thickness C of the separator. The porosity D (%) of the layer is the mass Wi (g / cm ² ) of the component i per unit area, the density di (g / cm ³ ) of the component i, and the heat resistance for each component i constituting the heat-resistant insulating layer. Using the thickness t (cm) of the insulating layer, it can be obtained from the following formula (3): When the porosity of the heat-resistant insulating layers on both sides is different, the average value of these is calculated as the porosity D (% ) Value.

The heat-resistant insulating layer 3 is provided on both sides of the resin porous substrate 2 in the stacking direction, that is, the direction in which the positive electrode, the negative electrode, and the electrolyte layer 17 are stacked. Moreover, it is preferable that the heat-resistant insulating layers 3 formed on both surfaces of the resin porous substrate 2 are directly laminated on the opposing surfaces of the heat-resistant insulating layers as shown in FIG. Furthermore, it is preferable that the heat-resistant insulating layer 3 is formed on both surfaces of the resin porous substrate 2. As shown in FIG. 3, the heat-resistant insulating layer 3 may be a single layer or a plurality of layers. Further, when the heat-resistant insulating layer 3 is composed of a plurality of layers, they may be formed of different materials.

Hereinafter, the separator according to this embodiment will be described in more detail.

(Resin porous substrate)
Examples of the resin porous substrate 2 include a porous sheet, a woven fabric, or a nonwoven fabric containing an organic resin that absorbs and holds an electrolyte. As the organic resin contained in the resin porous substrate, it is preferable to use polyolefins such as polyethylene (PE) and polypropylene (PP); polyimides such as polyimide and aramid; and polyesters such as polyethylene terephthalate (PET). Further, the average value of pore diameters (average pore diameter) of pores formed in the resin porous substrate is preferably 10 nm to 1 μm. The pore diameter formed in the resin porous substrate can be determined by, for example, a nitrogen gas adsorption method. The thickness of the porous resin substrate is preferably 1 μm to 200 μm. Further, the porosity of the resin porous substrate is desirably 20 to 90%.

The resin porous substrate will be described in more detail. A porous sheet that can be used as a resin porous substrate is a microporous membrane composed of a microporous polymer. Examples of such polymers include polyolefins such as polyethylene (PE) and polypropylene (PP); laminates having a three-layer structure of PP / PE / PP, polyimide, and aramid. In particular, a polyolefin-based microporous membrane is preferable because it has a property of being chemically stable with respect to an organic solvent and can reduce the reactivity with an electrolytic solution.

The thickness of the porous sheet cannot be uniquely defined because it varies depending on the application. However, in the use of a secondary battery for driving a motor of a vehicle, it is desirable that the thickness is 4 to 60 μm in a single layer or multiple layers. The fine pore diameter of the porous sheet is usually about 10 nm, but is preferably 1 μm or less at maximum. The porosity of the porous sheet is preferably 20 to 80%.

As the woven or non-woven fabric that can be used as the resin porous substrate, polyester such as polyethylene terephthalate (PET); polyolefin such as PP or PE; polyimide, aramid, or the like can be used. The bulk density of the woven fabric or the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated electrolytic solution. The porosity of the woven or non-woven fabric is preferably 50 to 90%. Furthermore, the thickness of the woven or non-woven fabric is preferably 5 to 200 μm, particularly preferably 5 to 100 μm. If the thickness is 5 μm or more, the electrolyte retainability is good, and if it is 100 μm or less, the resistance is difficult to increase excessively.

The method for preparing the resin porous substrate is not particularly limited. When the resin porous substrate is a polyolefin-based microporous membrane, for example, the polyolefin is dissolved in a solvent and then extruded into a sheet, then the solvent is removed, and the resin porous substrate is prepared by a method of performing uniaxial stretching or biaxial stretching. Can do. In addition, as a solvent, paraffin, liquid paraffin, paraffin oil, tetralin, ethylene glycol, glycerin, decalin, etc. can be used.

(Heat-resistant insulating layer (heat-resistant insulating porous layer))
In this embodiment, as the material of the heat resistant particles constituting the heat resistant insulating layer, a material having a high heat resistance having a melting point or a heat softening point of 150 ° C. or higher, preferably 240 ° C. or higher is used. By using such a material having high heat resistance, it is possible to effectively prevent the separator from contracting even when the battery internal temperature reaches around 200 ° C. As a result, it is possible to prevent induction of a short circuit between the electrodes, and thus it is possible to obtain a battery in which performance deterioration due to temperature rise hardly occurs. In the present specification, the “thermal softening point” refers to a temperature at which a heated substance softens and begins to deform, and refers to a Vicat softening temperature. In addition, although the upper limit of melting | fusing point or heat softening point of a heat-resistant particle | grain is not specifically limited, For example, it can be 1500 degrees C or less.

The heat-resistant particles have electrical insulation properties, are stable to solvents and electrolytes used in the production of the heat-resistant insulating layer, and are electrochemically stable that are not easily oxidized and reduced in the battery operating voltage range. It is preferable that The heat-resistant particles may be organic particles or inorganic particles, but are preferably inorganic particles from the viewpoint of stability. The heat-resistant particles are preferably fine particles from the viewpoint of dispersibility, and fine particles having an average secondary particle diameter (median diameter, D50) of, for example, 100 nm to 4 μm, preferably 300 nm to 3 μm, more preferably 500 nm to 3 μm. Is used. The average secondary particle diameter (median diameter) can be determined by a dynamic light scattering method. Further, the shape of the heat-resistant particles is not particularly limited, and may be a nearly spherical shape, or may be a plate shape, a rod shape, or a needle shape.

The inorganic particles (inorganic powder) having a melting point or thermal softening point of 150 ° C. or higher are not particularly limited. However, as inorganic particles, for example, iron oxide (FeO), SiO ₂ , Al ₂ O ₃ , aluminosilicate (aluminosilicate), TiO ₂ , BaTiO ₂ , ZrO ₂ and other inorganic oxides; aluminum nitride, silicon nitride Inorganic nitrides such as: Calcium fluoride, barium fluoride, barium sulfate and other insoluble ion crystals; Silicon, diamond and other covalently bonded crystals; and Montmorillonite clay and other particles. The inorganic oxide may be a mineral resource-derived substance such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, mica, or an artificial product thereof. The inorganic particles may be particles that are made electrically insulating by covering the surface of the conductive material with an electrically insulating material such as the above-described inorganic oxide. As the conductive material, metal; SnO _2, tin - conductive oxide such as indium oxide (ITO); carbon black, and the like can be exemplified carbonaceous material such as graphite. Among these, the inorganic oxide particles can be easily applied as a water-dispersed slurry on the resin porous substrate, and therefore, a separator can be produced by a simple method, which is preferable. Among the inorganic oxides, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), and aluminosilicate (aluminosilicate) are particularly preferable.

Organic particles (organic powder) having a melting point or thermal softening point of 150 ° C. or higher include crosslinked polymethyl methacrylate, crosslinked polystyrene, crosslinked polydivinylbenzene, crosslinked styrene-divinylbenzene copolymer, polyimide, melamine resin, phenol Examples thereof include various crosslinked polymer particles such as resin and benzoguanamine-formaldehyde condensate. Examples of the organic particles include heat-resistant polymer particles such as polysulfone, polyacrylonitrile, polyaramid, polyacetal, and thermoplastic polyimide. Moreover, the organic resin constituting these organic particles is a mixture of the above-exemplified materials, a modified body, a derivative, a copolymer (random copolymer, alternating copolymer, block copolymer, graft copolymer), It may be a crosslinked body (in the case of the above heat-resistant polymer fine particles). Among these, from the viewpoint of industrial productivity and electrochemical stability, it is desirable to use polymethyl methacrylate and polyaramid particles as organic particles. By using such organic resin particles, a separator mainly composed of a resin can be manufactured, and thus a light battery as a whole can be obtained.

In addition, the above heat-resistant particle | grains may be used individually by 1 type, and may be used in combination of 2 or more types.

The thickness of the heat-resistant insulating layer constituted by using the heat-resistant particles is appropriately determined according to the type of battery, application, etc., and is not particularly limited. However, as the thickness of the heat-resistant insulating layer, for example, the total thickness of the heat-resistant insulating layers formed on both surfaces of the resin porous substrate is preferably about 5 to 200 μm. In applications such as secondary batteries for driving motors such as electric vehicles and hybrid electric vehicles, the total thickness of the heat-resistant insulating layers formed on both surfaces of the resin porous substrate is 5 to 200 μm, preferably 5 to 20 μm. More preferably, it is 6 to 10 μm. When the thickness of the heat-resistant insulating layer is in such a range, high output performance can be secured while increasing the mechanical strength in the thickness direction (stacking direction).

Further, the thickness ratio A ′ / A ″ of the heat-resistant insulating layer formed on both surfaces of the resin porous substrate may be set so as to satisfy the formula (1), but is preferably 1.2 or less, More preferably, it is 1.1 or less, that is, the thickness ratio A ′ / A ″ of the heat-resistant insulating layer is preferably 1.0 to 1.2, more preferably 1.0 to 1.1. More preferred. The thicknesses of the heat-resistant insulating layers formed on both surfaces of the resin porous substrate are preferably the same as much as possible. Thereby, the two heat-resistant insulating layers can evenly hold both surfaces of the resin porous substrate, and curling of the separator can be suppressed.

The porosity of the heat-resistant insulating layer composed of the heat-resistant particles is not particularly limited, but is preferably 40% or more, more preferably 50% or more from the viewpoint of ion conductivity. Moreover, if the porosity is 40% or more, the retainability of the electrolyte (electrolytic solution, electrolyte gel) is improved, and a high-power battery can be obtained. The porosity of the heat-resistant insulating layer is preferably 70% or less, more preferably 60% or less. When the porosity of the heat-resistant insulating layer is 70% or less, sufficient mechanical strength is obtained, and the effect of preventing a short circuit due to foreign matter is high.

Furthermore, the content of the heat-resistant particles in the heat-resistant insulating layer is preferably 90 to 100% by mass, and more preferably 95 to 100% by mass. Thereby, the two heat-resistant insulating layers can uniformly hold both surfaces of the porous resin substrate.

(Manufacturing method of separator)
The manufacturing method of the separator of this embodiment is not particularly limited. However, as a manufacturing method, for example, a slurry-like composition for a heat-resistant insulating layer containing heat-resistant particles having a melting point or a heat softening point of 150 ° C. or higher is applied on both surfaces of a resin porous substrate, and then dried. The method is used.

The heat-resistant insulating layer composition is obtained by dispersing heat-resistant particles in a solvent, and may further contain an organic binder or the like as necessary. Examples of the organic binder for enhancing the shape stability of the heat resistant insulating layer include carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, and the like. When an organic binder is included, the amount of the organic binder used is preferably 10% by mass or less, more preferably 5% by mass or less, with respect to the total mass of the heat-resistant particles and the organic binder. The solvent is not particularly limited as long as it can uniformly disperse the heat-resistant particles. However, examples of the solvent include water; aromatic hydrocarbons such as toluene; furans such as tetrahydrofuran; ketones such as methyl ethyl ketone, methyl isobutyl ketone and acetone; N-methylpyrrolidone; dimethylacetamide; dimethylformamide; Examples include ethyl acetate. In order to control the interfacial tension, ethylene glycol, propylene glycol, monomethyl acetate, or the like may be appropriately added to these solvents. In particular, when inorganic oxide particles are used as the heat-resistant particles, a heat-resistant insulating layer can be easily produced by preparing an aqueous dispersion slurry using water as a solvent. Further, the composition for a heat-resistant insulating layer is preferably prepared so that the solid content concentration is 30 to 60% by mass.

Basis weight at the time of applying the resin porous substrate in heat insulating layer composition is not particularly limited, preferably 5 ~ 20g / m ^2, more preferably from 9 ~ 13g / m ^2. In this case, “weight” refers to the weight (g / m ² ) of the heat-resistant insulating layer composition per unit area of the resin porous substrate. If it is the said range, the heat resistant insulating layer which has a suitable porosity and thickness will be obtained. The coating method is not particularly limited, and examples thereof include a knife coater method, a gravure coater method, a screen printing method, a Mayer bar method, a die coater method, a reverse roll coater method, an ink jet method, a spray method, and a roll coater method.

The method of drying the heat-resistant insulating layer composition after coating is not particularly limited, and for example, a method such as warm air drying is used. The drying temperature is, for example, 30 to 80 ° C., and the drying time is, for example, 2 seconds to 50 hours.

The total thickness of the separator thus obtained is not particularly limited, but it can be generally used if it is about 5 to 30 μm. In order to obtain a compact battery, it is preferable to make it as thin as possible within a range in which the function as the electrolyte layer can be secured. Therefore, in order to contribute to the improvement of battery output by reducing the thickness, the total thickness of the separator is preferably 20 to 30 μm, more preferably 20 to 25 μm.

The electrolyte layer is not particularly limited as long as it is formed using the separator of the present embodiment. That is, the electrolyte layer of the present embodiment has the separator, and an electrolyte contained in the separator porous resin substrate and the heat-resistant insulating layer. Moreover, it is preferable that the electrolyte hold | maintained at an electrolyte layer contains lithium ion and is excellent in lithium ion conductivity.

Specifically, as the electrolyte layer, a separator containing an electrolytic solution having excellent ion conductivity can be used. Further, an electrolyte layer formed by impregnating, applying, spraying, etc. a gel electrolyte or the like into a separator can also be used.

(A) Electrolyte-containing separator In the electrolyte solution that can be infiltrated into the separator of this embodiment, the electrolytes include LiClO ₄ , LiAsF ₆ , LiPF ₅ , LiBOB, LiCF ₃ SO ₃ and Li (CF ₃ SO ₂ ) _2. At least one of N can be used. Examples of the solvent for the electrolyte include ethylene carbonate (EC), propylene carbonate, diethyl carbonate (DEC), dimethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1, At least one kind selected from ethers composed of 3-dioxolane and γ-butyllactone can be used. It is preferable to use an electrolytic solution in which the electrolyte is dissolved in the solvent and the concentration of the electrolyte is adjusted to 0.5 to 2M. However, the present invention is not limited to these.

Since the separator of the present embodiment described above is used as the separator, the description thereof is omitted here.

The amount of the electrolytic solution retained in the separator by impregnation or the like may be impregnated or applied to the separator's liquid retention capacity range, but may be impregnated beyond the liquid retention capacity range. This is because, for example, in the case of a bipolar battery, a resin can be injected into the electrolyte seal portion to prevent the electrolyte solution from exuding from the electrolyte layer, so that it can be impregnated as long as it can be retained in the separator of the electrolyte layer. is there. Similarly, in the case of a non-bipolar battery, since the battery element can be enclosed in the battery exterior material to prevent the electrolyte from leaking out from the inside of the battery exterior material, impregnation is performed as long as the liquid can be retained inside the battery exterior material. Is possible. The electrolytic solution can be impregnated in the separator by a conventionally known method such as completely sealing after injecting by a vacuum injection method or the like.

(B) Gel electrolyte layer The gel electrolyte layer of the present invention is obtained by impregnating and applying the gel electrolyte to the separator of the present embodiment.

The gel electrolyte has a configuration in which the above liquid electrolyte (electrolytic solution) is injected into a matrix polymer made of an ion conductive polymer. Examples of the ion conductive polymer used as the matrix polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. In such a polyalkylene oxide polymer, an electrolyte salt such as a lithium salt can be well dissolved.

The ratio of the liquid electrolyte (electrolytic solution) in the gel electrolyte is not particularly limited, but is preferably about several mass% to 98 mass% from the viewpoint of ionic conductivity. In the present embodiment, the gel electrolyte having a large amount of electrolytic solution having a ratio of the electrolytic solution of 70% by mass or more is particularly effective.

The gel electrolyte matrix polymer can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, a polymerization treatment may be performed on a polymerizable polymer for forming a polymer electrolyte using an appropriate polymerization initiator. Examples of the polymerization treatment include thermal polymerization, ultraviolet polymerization, radiation polymerization, and electron beam polymerization. For example, PEO or PPO can be used as the polymerizable polymer.

The thickness of the electrolyte layer is not particularly limited, but is basically about the same as or slightly thicker than the thickness of the separator of this embodiment. If the thickness of the electrolyte layer is usually about 5 to 30 μm, it can be used.

In the present invention, the electrolyte of the electrolyte layer may contain various conventionally known additives as long as the effects of the present invention are not impaired.

[Current collector and lead]
A current collecting plate may be used for the purpose of extracting the current outside the battery. The current collector plate is electrically connected to the current collector and the lead, and is taken out of the laminate sheet that is a battery exterior material.

The material constituting the current collector plate is not particularly limited, and a known highly conductive material can be used as a current collector plate for a lithium ion secondary battery. As a constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. As a constituent material of the current collector plate, aluminum, copper, and the like are particularly preferable from the viewpoint of light weight, corrosion resistance, and high conductivity. In addition, the same material may be used for a positive electrode current collecting plate and a negative electrode current collecting plate, and a different material may be used.

∙ Use positive terminal lead and negative terminal lead as required. As a material for the positive electrode terminal lead and the negative electrode terminal lead, a terminal lead used in a known lithium ion secondary battery can be used. In addition, it is preferable to cover the part taken out from the battery outer packaging material 29 with a heat-shrinkable heat shrinkable tube or the like. Thereby, it can prevent affecting a product (for example, automobile parts, especially electronic equipment etc.) by contacting with peripheral equipment, wiring, etc., and leaking electricity.

[Battery exterior materials]
As the battery exterior material 29, a known metal can case can be used. Moreover, as the battery exterior material 29, a bag-like case using a laminate film containing aluminum that can cover the power generation element can be used. As the laminate film, for example, a film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used, but is not limited thereto. A laminate film is desirable from the viewpoint that it is excellent in high output and cooling performance, and can be suitably used for a battery for large equipment for EV and HEV.

In addition, said lithium ion secondary battery can be manufactured with a conventionally well-known manufacturing method.

[Appearance structure of lithium ion secondary battery]
FIG. 4 is a perspective view showing the appearance of a flat plate type lithium ion secondary battery.

As shown in FIG. 4, the stacked battery 10 has a rectangular flat shape, and a positive electrode current collector plate 25 and a negative electrode current collector plate 27 for taking out electric power are drawn out from both sides thereof. Yes. The power generation element 21 is wrapped by the battery outer material 29 of the stacked battery 10, and the periphery of the battery outer material 29 is heat-sealed. The power generation element 21 is sealed with the positive electrode current collector plate 25 and the negative electrode current collector plate 27 pulled out to the outside. The power generation element 21 is formed by laminating a plurality of single battery layers (single cells) 19 including a positive electrode (positive electrode active material layer 13), an electrolyte layer 17 and a negative electrode (negative electrode active material layer 15) shown in FIG. .

Further, the drawing of the positive electrode current collector plate 25 and the negative electrode current collector plate from the battery exterior material 29 shown in FIG. 4 is not particularly limited. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 may be drawn from the same side. Further, the positive electrode current collector plate 25 and the negative electrode current collector plate 27 may be divided into a plurality of parts and taken out from each side. That is, the extraction of the positive electrode current collector plate 25 and the negative electrode current collector plate from the battery exterior material 29 is not limited to that shown in FIG.

In the above embodiment, a lithium ion secondary battery is exemplified as the electric device. However, the present invention is not limited to this, and can be applied to other types of secondary batteries and further to primary batteries. Moreover, it can be applied not only to batteries but also to capacitors.

Hereinafter, the present invention will be specifically described based on examples. The technical scope of the present invention is not limited only to these examples.

[Example 1]
An aqueous dispersion of aluminosilicate fine particles, which is a composition for a heat-resistant insulating layer, was applied to both surfaces of a polyethylene (PE) microporous film, which is a resin porous substrate, using a blade coater. Here, the polyethylene microporous membrane has a thickness of 18.9 μm and a porosity of 42%. The aluminosilicate fine particles have an average secondary particle diameter of 1 μm and a melting point of 1000 ° C. or higher. Furthermore, the solid content concentration of the aqueous dispersion of aluminosilicate fine particles is 40% by mass. Then, it dried with warm air, formed the heat-resistant insulating layer, and produced the separator with a heat-resistant insulating layer. This separator with a heat-resistant insulating layer was formed in a roll shape having a width of 200 mm.

The heat-resistant insulating layer was coated so that the thickness on one side was 2.8 μm or more, but finished with a thick side of 3.1 μm and a thin side of 2.5 μm. The obtained separator with a heat-resistant insulating layer had a total thickness of 24.5 μm, and the porosity of the heat-resistant insulating layer was 47%.

[Examples 2 to 12, Comparative Examples 1 to 4]
In the same manner as in Example 1, a separator having a porous resin substrate and a heat-resistant insulating layer shown in Table 1 was produced.

However, in Examples 2, 3, 6 and 11 and Comparative Example 2, a polypropylene (PP) microporous film (porosity 55%) was used as the resin porous substrate instead of the polyethylene microporous film.

In Examples 4, 5, 7, 9, and 10, and Comparative Example 3, a polyethylene (PE) microporous membrane (porosity 52) was used as the resin porous substrate instead of the polyethylene microporous membrane (porosity 42%). %) Was used.

In Example 8, a non-woven fabric made of polyethylene terephthalate (PET) was used as the resin porous substrate instead of the polyethylene microporous membrane. The nonwoven fabric made of polyethylene terephthalate has a film thickness of 11.1 μm and a porosity of 48%.

In Comparative Examples 1, 4 and 5, a polyethylene (PE) microporous film (porosity 42%) was used as the resin porous substrate.

In Examples 2 to 7, Examples 10 and 11, and Comparative Examples 2 and 3, high-purity alumina particles were used as the heat-resistant particles instead of the aluminosilicate of Example 1. The high purity alumina particles have an average secondary particle diameter of 1.5 μm and a melting point of 1000 ° C. or higher.

In Example 8, a methyl ethyl ketone dispersion of colloidal silica particles was used in place of the aluminosilicate aqueous dispersion of Example 1. The colloidal silica particles have an average secondary particle diameter of 0.4 μm and a melting point of 1000 ° C. or higher. The methyl ethyl ketone dispersion has a solid content concentration of 30% by mass.

In Example 9, instead of the aluminosilicate aqueous dispersion of Example 1, crosslinked polymethyl acrylate particles were used. The crosslinked polymethyl acrylate particles have an average secondary particle diameter of 1 μm and a heat softening point of about 160 ° C.

In Example 12, an NMP dispersion of an aromatic polyamide (aramid) resin was used as the heat-resistant insulating layer composition, and ethylene glycol was added to form a porous layer.

[Comparative Example 5]
A separator was produced in the same manner as in Example 1 except that the heat-resistant insulating layer was applied to one side of the resin porous substrate.

The thicknesses A ′, A ″ (μm), the total thickness C (μm), and the porosity D (%) of the heat-resistant insulating layer in the obtained separators of Examples 1 to 12 and Comparative Examples 1 to 5 are shown. The results are summarized in Table 1.

[Curl height]
The curl height of the separator produced in each example and comparative example was measured by the following procedure. First, as shown in FIG. 5, the separator was cut out from the separator roll so as to be substantially square, placed on a horizontal plane, and then static electricity was removed by stroking with a static elimination brush twice. Thereafter, the heights of the eight positions A to H in FIG. 5 that were lifted from the horizontal plane in 60 seconds were measured, and the maximum value was taken as the curl height (mm). When it was rolled up, it was unwound and stretched upward, and its height was taken as the measured value.

[Battery evaluation]
Aluminum foil was prepared as a positive electrode current collector, and copper foil was prepared as a negative electrode current collector. A positive electrode active material slurry was prepared using lithium cobalt nickel manganate (LiNi _0.33 Co _0.33 Mn _0.33 O ₂ ) as the positive electrode active material. On the other hand, a negative electrode active material slurry was prepared using artificial graphite as the negative electrode active material. The positive electrode active material slurry and the negative electrode active material slurry were applied to an aluminum foil as a positive electrode current collector and a copper foil as a negative electrode current collector, respectively, dried, and then roll pressed to produce a positive electrode and a negative electrode. The separator prepared in each Example and Comparative Example was sandwiched between the positive electrode and the negative electrode prepared above, a non-aqueous electrolyte was injected, and sealed in a laminate sheet to prepare an evaluation battery. As the non-aqueous electrolyte, a solution obtained by dissolving LiPF ₆ as a solute at a concentration of 1.0 ml / L in a mixed solvent of ethylene carbonate: ethyl methyl carbonate = 1: 2 (volume ratio) was used.

After the battery was fabricated, the first charge / discharge was performed and the battery capacity was measured. The initial discharge capacity was 20 mAh. In this battery, the discharge capacity at 4.0 mA and the discharge capacity at 50 mA were measured, and the ratio (discharge capacity at 50 mA / discharge capacity at 4.0 mA) was determined as a rate characteristic (rate ratio) ( %).

Table 1 shows the results of rate characteristics of the examples and comparative examples. FIG. 6 shows the relationship between the parameter X and the curl height, and FIG. 7 shows the relationship between the parameter Y and the curl height and rate characteristics.

The separators produced in Examples 1 to 12 had a parameter X value of 0.15 or more. In each of Examples 1 to 12, the curl height was 5 mm or less, and there was no problem even when the plates were laminated by a flat plate continuous laminator, and good products were obtained continuously. Here, in the flat plate continuous laminator, the processes including cutting with a hot blade, conveyance with a porous adsorption pad, and lamination with a four-point clamp are repeated several tens of times, and the end portions are laminated without being folded. It was confirmed. In addition, the process including the cutting | disconnection with a hot blade, the conveyance by a porous adsorption pad, and the lamination | stacking by a 4-point clamp was performed in about 3 seconds.

In the separators of Comparative Examples 1 to 4, in the flat plate continuous laminator, the separator was frequently turned during the conveyance of the separator onto the electrode. Therefore, when it was made into a laminated body, it was laminated in a state where the separator was stepped on, making it unusable. In particular, in Comparative Example 5 on which single-sided coating was performed, curling immediately occurred at the time of cutting, and conveyance itself was impossible.

Regarding the rate characteristics, in the separators produced in Examples 1 to 9, the parameter Y was 0.3 to 0.7, and a sufficient output exceeding 85% was obtained. On the other hand, in Examples 10 to 12 in which the value of the parameter Y exceeds 0.7, the rate characteristics are less than 85%, and the product performance is slightly insufficient.

From the above results, it was found that curling can be suppressed by adjusting the thickness of the heat-resistant insulating layer relative to the total thickness of the separator and balancing the thickness of the heat-resistant insulating layers on both sides.

Furthermore, in addition to the above conditions, it was found that a battery with high output characteristics can be obtained at the same time by adjusting the thickness and porosity of the heat-resistant insulating layer.

The entire contents of Japanese Patent Application No. 2011-133893 (filing date: June 22, 2011) are incorporated herein by reference.

As mentioned above, although the content of the present invention has been described according to the embodiments, the present invention is not limited to these descriptions, and it is obvious to those skilled in the art that various modifications and improvements are possible.

In the separator with a heat-resistant insulating layer of the present invention, the balance of shrinkage stress of the heat-resistant insulating layers on both sides is improved by controlling the thickness and the total thickness of the heat-resistant insulating layers on both sides. Further, the balance between the internal stress of the resin porous substrate and the shrinkage stress of the heat-resistant insulating layer is improved. For this reason, curling is unlikely to occur during lamination, and a highly reliable electric device can be stably manufactured.

1 Separator with heat-resistant insulating layer (separator)
2 Resin porous substrate 3 Heat resistant insulating layer 4 Positive electrode 5 Negative electrode 10 Stacked battery (lithium ion secondary battery)
DESCRIPTION OF SYMBOLS 11 Positive electrode collector 12 Negative electrode collector 13 Positive electrode active material layer 15 Negative electrode active material layer 17 Electrolyte layer 19 Single cell layer 21 Power generation element 25 Positive electrode current collector plate 27 Negative electrode current collector plate 29 Battery exterior material (laminate film)

Claims (9)

1. A porous resin substrate;
   A heat-resistant insulating layer comprising heat-resistant particles formed on both surfaces of the resin porous substrate and having a melting point or thermal softening point of 150 ° C. or higher;
   With
   The parameter X represented by Formula 1 is 0.15 or more, and a separator with a heat-resistant insulating layer for an electrical device:
   

   

   
   In the formula, A ′ and A ″ are the thicknesses (μm) of the respective heat-resistant insulating layers formed on both surfaces of the porous resin substrate, where A ′ ≧ A ″, and C is with the heat-resistant insulating layer. This is the total thickness (μm) of the separator.
2. 2. The separator with a heat-resistant insulating layer according to claim 1, wherein the parameter Y represented by Formula 2 is in the range of 0.3 to 0.7:
   

   

   
   In the formula, D is the porosity (%) of the heat-resistant insulating layer.
3. The separator with heat-resistant insulating layer according to claim 1 or 2, wherein the parameter X is 0.20 or more.
4. The separator with a heat-resistant insulating layer according to any one of claims 1 to 3, wherein the heat-resistant particles are inorganic oxide particles.
5. 4. The separator with a heat resistant insulating layer according to claim 1, wherein the heat resistant particles are organic resin particles. 5.
6. The separator with a heat-resistant insulating layer according to any one of claims 1 to 5, wherein a porosity of the heat-resistant insulating layer is 40 to 70%.
7. The total thickness of the heat-resistant insulating layer is 5 to 200 μm, and the thickness ratio (A ′ / A ″) of the heat-resistant insulating layer is 1.0 to 1.2. The separator with a heat-resistant insulating layer according to any one of the above.
8. A separator with a heat-resistant insulating layer according to any one of claims 1 to 7,
   An electrolyte contained inside the resin porous substrate and the heat-resistant insulating layer of the separator with the heat-resistant insulating layer;
   An electrolyte layer for an electrical device, comprising:
9. An electric device comprising the separator with a heat-resistant insulating layer according to any one of claims 1 to 7.

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